Patent GB-294620-A (GB)
Title: New or improved apparatus for profiling gear teeth
IPC: B23F5/02
Filed: 1927-09-30
Abstract: 294,620. Lees-Bradner Co., (Assignees of Schurr, C. H.). July 29, 1927, [Convention date]. Gear - cutting. - In apparatus for producing gear teeth by rolling a gear blank relatively to a rotating tool, the generating movements may be modified by impacting supplemental motions to the blank or tool to produce predetermined modification of the theoretical involute tooth profile. The guideways 3 carry a slide 4, reciprocated by a rod 5 and carrying the work spindle 8 in a housing 9. One end of the work-spindle carries an accurate involute mastergear 10 engaging a master-rack 50 and the other end carries the blank 12 which is located beneath an adjustable planular grinding-wheel 15 which is preferably set so that its operative surface lies in the plane of one of the master-rack teeth. The rolling of the master-gear on its rack imparts the required generating movement to the blank, the teeth of which are rolled successively past the grinding-wheel. The indexing of the blank is effected in a manner similar to that described in Specification 279,046. the rack 50 consisting of a fixed part and a movable part and the movable part being moved to effect indexing by mechanism actuated from a cam 35 when the blank has been moved clear of the tool after the operation. Modification of the gear profile is obtained by imparting timed movement to the housing 20 carrying the generating rack, thus advancing the blank in a varying degree with respect to the tool to give a profile such as 45, Fig. 12, instead of the involute profile 41. The housing 20 is adjustably secured to a slide 54 which is movable on guides 53 in a vertically-adjustable bracket 150. A pair of abutments 62, 63 mounted on the slide 54 accommodate a block 64 bored to receive an eccentric 65 mounted on a shaft 66 which rotates in bearings in the bracket 150. The shaft 66 carries an adjustable depending arm 69 having a roller engaging an inclined cam track 80 secured to the housing 9. Thus in operation during the reciprocation of the slide 4, the arm 69 is rocked by the cam 80 to rotate the eccentric shaft 66 and impart the required profilemodifying movement to the rack-holder 20. Preferably the abutment 62 is held against the block 64 by a spring 90, so as to eliminate backlash. In order to produce the profile 45, Fig. 12, the mechanism is first adjusted so that the eccentric 65 is in the position of symmetry, Fig. 8, where the grinding-wheel is in contact with the unmodified portion 44 of the tooth profile. In another modification, Fig. 13, the relieving of the tooth begins at the root and continues progressively to a maximum at the tip of the tooth and in this case the eccentric is set to its symmetrical position when the grinding-wheel engages the root of a tooth. Another modification of the profile may be made by relieving the tooth progressively from tip to root. By rotating the eccentric through 180‹ the tooth may be ground so that the modified curve lies outside or partially outside the true involute. By arranging the cam track 80 in a horizontal position, ordinary involute teeth without modification may be ground. The cam track may also be shaped as shown in Fig. 7, end in this case the upturned portion 102 of the cam will cause the profile to be modified by removing the extreme point 100, Fig. 15. In all cases the eccentric may be replaced by a cam or other mechanism for giving the profile-modifying movement. The machine may also be modified by imparting the supplementary movement to the grinding-wheel instead of to the rack. The Specification as open to inspection under Sect. 91 (3) (a) describes also the application of the invention. The invention is applicable to machines having other types of generating mechanism such as flexible-band mechanism or cam-mechanism of the type shown in Fig. 19 (Cancelled), wherein the blank 110 is rolled by means of a profiled cam 112 coacting with abutments 115. The invention is also applied to the production of bevel-gearing. In Fig. 20 (Cancelled) the master bevel-gear 117 rolls on a crownwheel segment 116 to give the generating movement to the blank 118, and the modification of the profile is produced by oscillating the segment 116 about its centre 119. This subject-matter does not appear in the Specification as accepted.